Inkjet printers eject drops of ink through an array of nozzles to effect printing on a media substrate. The nozzles are typically formed on a silicon wafer substrate using semiconductor fabrication techniques. Each nozzle is a MEMS (micro electro-mechanical systems) device driven by associated drive circuitry formed on the same silicon wafer substrate. The MEMS nozzle devices and associated drive circuitry formed on a single nozzle is commonly referred to as a printhead integrated circuit (IC).
Traditional inkjet printers use scanning inkjet printheads. These have a single printhead IC that traverses back and forth across the width of a page as the printer indexes the page along. The Applicant has developed a range of pagewidth printheads. These printheads use a series of printhead IC's mounted end to end to provide an array of nozzles that extends the entire width of the page. Instead of scanning back and forth, the printhead remains stationary in the printer as the page is fed past. This allows much higher print speeds but is more complicated in terms of controlling the operation of a much larger array of nozzles.
As the printhead IC's have micron-scale structures that eject very small drops of ink (in the pico-litre range), any changes in the viscosity of the ink can have a significant effect on the ejection characteristics of the nozzle. A large array of nozzles, such as a pagewidth array, is likely to have appreciable temperature variations along its length. Unfortunately, the ink viscosity is temperature dependent and therefore the ink viscosity can also vary along the length of the nozzle array. The viscosity variations can affect the drop ejection characteristics and therefore lead to visible artifacts in the printed page.